This invention relates to earth boring and more particularly to roller reamers useful in the drill strings employed in the rotary system of drilling, either immediately above the drill bit or higher up in the string, e.g. between drill collars, for maintaining the hole full gage.
Conventional roller reamers employ a plurality of rollers each mounted to rotate on a shaft. Each shaft is mounted at the periphery of a body that is provided at its ends with threaded connectors for joining with other parts of a rotary drill string. The space between each roller and shaft is lubricated by the drilling fluid (air, water, mud, oil) passing through the body and back up the earth bore outside the body.